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  2. SME

    Rob's Amp tests

    Wow, these are nice! If I may make a suggestion for the comparisons of power at different frequencies: plot these in units of dB instead of watts! Use 1000 Hz as a reference, so it's always "0 dB" at 1000 Hz and will typically be small or negative at the other frequencies. (So maybe use "+1 dB" for the top of the Y-axis.) I think this will convey information that is much more useful to the reader as it clarifies exactly out much output you lose at some lower frequency. The formula to calculate this is as follows: dB(f) = 10 * log10( P(f) / P(1000) ) where dB(f) is the decibels at frequency 'f', and P(f) is the power at that frequency. dB(1000) should always be 0. Other graphs may also be more useful in decibel units, but decibel units only make sense when you have a meaningful reference point as above. When comparing different amps to one another, there isn't a good reference unless you choose one of them to compare everything else to. What do you think?
  3. Yesterday
  4. Which of the two styles would you guys prefer? Currently it shows values for 1khz for full range reference and 30Hz for deep bass reference, but I'm not even sure if that's needed. The data table clutters the graph a lot imo Evaluations will additionally have these: Which will react like this when they're presented with differing values for bust and peak:
  5. I've build 20 speakers with this dado size now and I see no reason why I'd need them to be deeper. And tbh, I don't think it's worth the hassle to make them when you don't have a CNC. You'll waste all the time you save on assembly with making the joints, possibly more.
  6. Last week
  7. 3mm?. Ok I was thinking most did more than that. Here is dsI1's dado if thats what they are called. I liked how it aids in assembly. I plan to make four so I figured I could make a jig for the "dado's," to help speed things up since I dont have a CNC.
  8. If you're talking about the dado joints, I always make them 3mm. That way I can cut them with max feed rates on my machine without worrying about inaccuracies too much. I never felt the need to make them bigger, they're mostly for easier positioning anyways, so 3mm is just fine for that. imo it doesn't matter stability wise, unless you expect to throw the cabs off a balcony often.
  9. Looked at making a template out of some scrap I have. I was hoping to recess the interior panels but wanted to know the depth others are recessing the panels? 1/4"/ 6mm? More?
  10. Well to be fair, I didn't double check and thought I was testing it into 2x8R, but instead the load bank was set to 4+2 Ohm...
  11. And the loadbank causes another casualty.. this time it's a Yamaha CR-600. Fuses are done for, but I hope everything else is still good. Measurements of my Hypex FA123 coming soon. Also ordered dedicated measurement equipment, since I already had trouble measuring the true performance of the Hypex amps... Fireface not clean enough. Getting the Cosmos ADC to use with a Topping D10b. Probably also going to get the Cosmos APU once it releases, which includes a 1khz notch and a preamp capable to delivering phantom power with lots of gain.
  12. @m_msThe CX800 is a sub developed by PK sound geared primarily towards electronic bass music. They are quite popular around here in the electronic music scene as having PK on your flyer generates a decent amount of hype for these types of shows. Now this is my own opinion based on experiences attending and throwing events on the BC West Coast but i have found they suffer from pretty bad port compression especially when pushed even reasonably hard. The bass essentially turns into a very boomy/chuffy/distorted one note kinda deal that's meant to be more felt than heard. When run properly arrayed and at a reasonable level they can sound pretty good for dubstep and drum&bass but i have found that the Skrams sound way tighter and punchier overall especially when it comes to house/techno/trance. Kick drums sound like actual kick drums where as on the cx800 the kick often loses its definition. At the end of the day i think the Skrams just do a better job overall at reproducing the original program material compared to the cx800 which impart more of their PK signature sound which sacrifices musicality for a more visceral feeling. There are many examples of ported double 18's out there that don't suffer from this type of problem, it just so happens that in our scene PK sound is used almost exclusively now a days so that's why people at the show noticed the difference in the Skrams.
  13. The QSC sub is larger and probably has more vent area compared to the Skram (when you block Skram ports to reach the same ~25Hz(?) tuning), meaning the QSC will be louder in the sub bass. Skram is front loaded, which means it's more efficient (louder) in the mid/upper-bass region. Skram is basically a band pass, which means it also masks some distortion. That would be the 3 main differences I guess. Skram has a rising native voltage sensitivity, while the QSC is probably pretty flat, going by my gut feeling here.
  14. I'll take my Mother's advice since I don't have much nice to say about one of the sub designs - if you are OK with building VS buying - I'd recommend the skram which has a smaller physical size.
  15. What's entailed in "people really appreciating the change" from double 18's to the Skram's? What's their feedback in more detail about any change in presentation here - is it simply about (more?) capacity, or does it come down to a perceived difference in presentation between the two box and driver types? @Ricci and others: Earlier this evening I was at local cinema watching 'Ghostbusters: Afterlife' (an amusing and largely successful follow-up to the '84 original), and was quite impressed by the bass impact and overall quality in the some 400 seat auditorium (with Atmos sound). Turns out their speakers are from QSC, and the subs they use are these: https://www.qsc.com/solutions-products/loudspeakers/cinema/subwoofers/sb-series/sb-15121/ I take it the 21" driver used here is the B&C 21SW152, and I believe I've read only two of them subs are used in this auditorium, though I find it hard to believe given how much the bass shook the whole locale. My question here is: how would the QSC sub compare to a Skram, say, with the same driver? Does the Skram make more outright use of both its front and back wave of the cone by comparison, or are they comparable to one another in overall SPL and presentation?
  16. First post on this forum, hi Guys! Really like all the content here and wish I would find it sooner. Looks like a pair of Ckrams is my next dream build. Big thanks for the design and detailed information! Frankly would prefer to build Scrams instead but the size and weight scares me (me and my spine, to be precise), don't think I can handle it. The biggest sub I built so far is vented B&C 18DS115-8 and so it's very interesting for me to see how a couple of NSW21 in Ckram cabs will sound. I will do some measurements after I'm done and will post here.
  17. Ricci how does the SW152 or IPAL look at 15hz and 20hz in simulation?
  18. Earlier
  19. The ds and sw are very similar in maximum output at their respective program powers. Bennett from B&C said you should only really use the sw if you need the higher power handling, otherwise it doesn't really matter which you pick so you should go for the cheaper one. Here is a hornresp of different drivers I've compared in the SKhorn
  20. I have them loaded with B&C 21ds115-4's. The soundsystem will be primarily used for small to medium sized outdoor parties where we might not always have adequate generator power so i figured the extra sensitivity of the 21ds115's might come in handy in certain cases. Although from what I understand the 21sw152 will go aprox 2-3db louder before power compression sets in? We also considered the new Eminence drivers however they seemed like they would be even harder to power properly in order to get the most out of them. The 44m20 amp has been absolutely incredible to use. I reckon it could power 8 Skrams in a pinch. We were using a Morin k30 before and although it had plenty of power it was extremely hard on our generators. The Linea seems to be much more efficient and also there was a noticeable improvement in the tightness of the bass produced. The linea amp also limits it current draw to match the power source which has been super handy as well as integrating seamlessly with our Linea ASC48 in System Engineer. Also wanted to say thanks for all your hard work and time you put in to sharing your knowledge and designs with us! This whole project has been extremely fun and rewarding and wouldn't be possible without resources such as these.
  21. How does the efficiency of the SKRAM compare to the Devastator (25%)? I'm very new to the world of horns, but am looking at them to achieve visceral, impactful bass that I can't get with sealed designs. I think the pant-flapping, chest-destroying insanity I am trying to achieve has something to do with efficiency.
  22. Nice setup Fink! Welcome to the forum. What drivers are you using in the Skrams? Also that Linea amp is supposed to be really good and beastly from what I hear.
  23. Had a pretty good outing this past weekend with our 4 Skrams and 2 Keystone subs for a 400 person event! Skrams are running off a Linea research 44m20. Tops are a pair of PM90 mid-highs which we just completed and powered by custom Hypex amps with a Linea Research ASC48 for sound processing . Was extremely limited on speaker placement because of the low tents and would have liked to run the Skrams on their sides or separated them slightly to spread out the coverage. Once we retire the keystones I think we may need to build another 2-4 Skrams to keep up with the Midhighs for bass heavy music but really impressed with the output overall! Got a lot of good feedback regarding the sound and people really appreciate the change from the usual PK cx800 double 18 subs that have over-saturated the market on the BC west coast.
  24. Thanks. That's a crying shame. Hopefully my Crowson will give me something a bit more to make this a better audio experience.
  25. Left hand side is the amplitude of the digital signal (with '0' at the top being the highest it can possibly go). The bottom is the frequency. Summarizing that graph: the loudest bass is -20dB at 40Hz, and it drops fast under that (10dB lower is about half as loud to your ears, so the bass at 20Hz is over half the volume of the bass at 40Hz). So ultimately you will not be blown away by any part of the low end in Shang-Chi. It's all relatively high in the frequency range, and not all that loud.
  26. OK. I admit I don't know how to read that chart. I guess I will just wait a see what's it like in my room.
  27. Well if you use the single vent open mode the tuning is around 15Hz if I recall. With 4 of them in a home with room gain below 30Hz, I'd expect strong output to 12 or 13Hz. You should have firepower to spare to use the lowest tuning. You would never do this in an outdoor PA type setting but in a home I'd likely run with only 1 or 2 vents open myself. As usual experimentation is key. YMMV. Chasing much below 15Hz is best handled by sealed/IB/shakers IMHO.
  28. Shang-Chi in the theater was nothing to write home about, but it was better than Black Widow and Eternals. All the Marvel movies released this year have been rather poor, bass wise.
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